A preliminary study on an upper ocean heat and salt content of the western Pacific warm pool region

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A preliminary study on an upper ocean heat and salt content of the western Pacific warm pool region Xiaoxin Yang1, 2, Xiaofen Wu1*, Zenghong Liu1, Chunxin Yuan3 1 State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, Ministry of

Natural Resources, Hangzhou 310012, China 2 Dalian Naval Academy, People’s Libration Army, Dalian 116000, China 3 College of Oceanic and Atmospheric Sciences, Ocean University of China, Qingdao 266100, China

Received 13 November 2017; accepted 28 December 2017 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract

On the basis of Argo profile data of the temperature and salinity from January 2001 to July 2014, the spatial distributions of an upper ocean heat content (OHC) and ocean salt content (OSC) of the western Pacific warm pool (WPWP) region and their seasonal and interannual variations are studied by a cyclostationary empirical orthogonal function (CSEOF) decomposition, a maximum entropy spectral analysis, and a correlation analysis. Probable reasons for variations are discussed. The results show the following. (1) The OHC variations in the subsurface layer of the WPWP are much greater than those in the surface layer. On the contrary, the OSC variations are mainly in the surface layer, while the subsurface layer varies little. (2) Compared with the OSC, the OHC of the WPWP region is more affected by El Niño-Southern Oscillation (ENSO) events. The CSEOF analysis shows that the OHC pattern in mode 1 has strong interannual oscillation, with eastern and western parts opposite in phase. The distribution of the OSC has a positive-negative-positive tripole pattern. Time series analysis shows that the OHC has three phase adjustments with the occurrence of ENSO events after 2007, while the OSC only had one such adjustment during the same period. Further analysis indicates that the OHC variations are mainly caused by ENSO events, local winds, and zonal currents, whereas the OSC variations are caused by much more complex reasons. Two of these, the zonal current and a freshwater flux, have a positive feedback on the OSC change in the WPWP region. Key words: ocean heat content, salt content, the western Pacific warm pool, Argo data Citation: Yang Xiaoxin, Wu Xiaofen, Liu Zenghong, Yuan Chunxin. 2019. A preliminary study on an upper ocean heat and salt content of the western Pacific warm pool region. Acta Oceanologica Sinica, 38(3): 60–71, doi: 10.1007/s13131-019-1399-1

1  Introduction The western Pacific warm pool (WPWP) is a region with high temperature relative to its periphery, and is one of the main heat sources driving global atmospheric motion. Changes in this region would have great influence on the global atmosphere and oceans, so the WPWP has always been a research focus in the atmospheric and marine sciences. Before the 1980s, owing to limited on-site observation data of environmental elements of the atmosphere and oceans, researchers could not monitor numerous physical and oceanographic phen